| Y | = | 100 | + | 4 5 | ( | Y | − | 250 | + | 70 | ) | + | 50 | + | 200 |
| 方程右边 = | 350 | + | 4 5 | ( | Y | − | 250 | + | 70 | ) |
| Y | = | 350 | + | 4 5 | ( | Y | − | 250 | + | 70 | ) |
| 方程右边 = | 350 | + | 4 5 | Y | − | 4 5 | × | 250 | + | 4 5 | × | 70 |
| = | 350 | + | 4 5 | Y | − | 200 | + | 56 |
| = | 206 | + | 4 5 | Y |
| Y | = | 206 | + | 4 5 | Y |
| Y | − | 4 5 | Y | = | 206 |
1 5 | Y | = | 206 |
| Y | = | 206 | ÷ | 1 5 |
| = | 206 | × | 5 |
| Y | = | 1030 |